The currently commercially available display devices usually provide different scenario setting modes, or allow a user to manually switch among multiple different image quality settings, or use a R/G/B/W histogram to determine features of image content to thereby automatically adjust the image contrast and brightness, or detect ambient light to adjust the backlight. In the prior art, the above adjustments are generally conducted according to information such as image contrast level or backlight environment. However, such information does not necessarily exactly describe the actual situation in which the display device is used.